This invention relates to a valve comprising a control spool movable in a valve bore and having a seal controlled by an actuating means.
In a valve of the kind shown in European patent application EP-A1No. 0 088 813, the seal is always compressed between the control spool and the wall of the valve bore so that friction between the seal and the wall of the valve bore adversely effects the degree of accuracy of the adjusting movement, the force required for producing adjustment, and the service life of the seal. However, this friction is necessary only when the seal is required to perform its sealing function.
A valve with an inflatable and deflatable seal is described in GFR patent application No. DE 33 32 363 which was published Mar. 28, 1985.
It would be desirable to provide an efficient and simple device for depressurizing pressurizable valve seals.